Derelict (i.e., lost or abandoned) commercial fishing gear, including nets and traps, can present safety, nuisance, and environmental impacts in freshwater and estuarine waters. Organisms, such as crabs and fish species, that become entrapped and thereafter die in derelict traps can act as an attractant to other animals, resulting in a self-baiting effect. Derelict fishing gear damages sensitive habitats and continues to capture both target and by-catch species, a process known as “ghost fishing”, leading to reduced fitness and delayed mortalities. Animals captured in derelict traps can experience starvation, cannibalism, infection, disease, and prolonged exposure to poor water quality (i.e., low dissolved oxygen).
The effect of derelict fishing gear is significant, and various states and regions have enacted measures to reduce the ecological and economic impacts of ghost fishing. For example, the state of Florida enacted regulations (CH 46-45, F.A.C., effective Jan. 1, 1995) establishing degradability requirements for blue crab traps. Traps are considered legal in Florida if a non-degradable trap lid (such as a metal panel) is secured to the trap using degradable materials such as jute twine or corrodible hooks. These materials have an unpredictable rate of degradation, and therefore cause prolonged ghost fishing after the gear becomes derelict. By the time the degradable connectors degrade, the trap lid is often not released due to factors unique to aquatic environments (e.g., barnacles and mussels create secondary attachment points). For example, many blue crab traps having such degradable connectors continue to trap and retain aquatic species long after the degradable part has degraded. This unpredictability related to degradable materials in aquatic environments also arises with lobster traps, nets, and other fishing gear.
To be functional, an aquatic trap must have an entrance into the enclosed space. For blue crab traps, the entrance is called a throat, which is typically a one-way funnel extending into the trap. For example, the state of Florida enacted regulations that specify the throat must be horizontally oriented and extend inward from a vertical wall less than 6 inches. (CH 46-45, F.A.C.) The aquatic trap often contains an additional opening no smaller than the throat. Unobstructed, this opening would serve as an exit for all species that enter the trap. Fisherman must obstruct the exit in compliance with local, state, and regional regulations. For instance, in Florida, the exit can be obstructed with a non-degradable trap lid connected to a trap via degradable jute twine or corrodible hooks. However, as noted previously, existing connectors and panels obstructing the exit fail to disconnect and thereby fail to release all captured species. This is because materials such as jute twine and corrodible hooks fail degrade in a predictable manner when immersed in aquatic environments. Therefore, ghost fishing continues despite best efforts by both elected officials and fishermen.
It is desirable for crab traps to have cull rings, also called escape rings or escape hatches, to allow small and juvenile crabs to escape the trap. Typically, such cull rings have an inside diameter of at least 2.25 inches. For example, the state of Florida requires all blue crab traps to have at least 3 unobstructed escape rings installed, each with a minimum inside diameter of 2.375 inches. (CH 46-45, F.A.C.) Lobster traps also are required to have escape hatches of varying sizes, with the size dependent on the jurisdiction. Applicants' previous applications, cited above and incorporated by reference herein, address a modified cull ring panel that incorporates a cull ring and obstructs an exit. When the cull ring panel is exposed to a marine environment, the panel degrades and the exit becomes unobstructed, whereby all species that enter the trap may escape.
There remains a need for improved fishing gear that, within a period of months after it becomes derelict, loses its ability to trap aquatic species. Ideally, any such implementation would not functionally degrade while being actively fished, but functionally degrade within a period of time after becoming derelict. We have identified a degradable plastic, polyhydroxyalkanoate (PHA), as an exceptional material for such purposes. The present invention modifies existing fishing gear with an apparatus that both connects to the gear and obstructs an exit when the equipment is being actively fished. When the gear becomes derelict, a component of the apparatus comprising a polyhydroxyalkanoate polymer degrades, whereby the exit is no longer obstructed. To reduce the economic burden on fishermen, it would be advantageous if the degradable component could be inexpensively incorporated into existing fishing gear, thereby providing the desired degradability without requiring the purchase of expensive new equipment.